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Discussion Starter #1
I posted this on the revolver forum and was advised to try the gunsmithing one.

Here is a question for those of you with detailed knowledge! What was the thread on the head end of the ejector rod on a 1900 New Service? I have a 4 1/2" NS in .455 Eley and the ejector rod head is missing. I am going to make a replacement head, but have to fit it onto the rod. The threaded end of the rod is very short, and I live in a metric country, so identifying the thread form is not a simple matter.

Thanks
Peter​
 

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If you don't get the info you need sooner, I will check my 1902 New Service and give what I learn. It will take e few of days because I am away from home. I have had enuf experience with the NS to know that the thread is not a common standard. I will give micrometer diameter measurement and threads per inch.
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I think the screw thread size for the ejector rod/cap is 6-40, or 0.138" diameter by 40 threads per inch. I measured the only example I can easily reach and it tends to confirm that. I can confirm the 40 tpi, but the ejector rod threads are worn somewhat and only measure 0.132" diameter, but the thread tops are rounded and worn, and the next largest screw thread size is 6-40. When Robert gets home, he can confirm or deny this.

Buck
 

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Peter,

If you can get the ejector rod cap from Gun Parts Corporation that is referenced in your other thread, it will fit the ejector rod of all New Services AFAIK. Anyway, it fits my reconstructed Model 1917, and I don't think the thread size was ever changed. Depending on how close to the original you want to come, you can machine the knurled surface smooth and add a cross-bored hole at the end, and re-blue.

Buck
 

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OK, finally got to the New Services in the back of the safe, and the ejector rod threads are 6-36, half way between the UNC 6-32 and UNF 6-40. I suppose that Colt wanted their own proprietary thread, but who knows why. I think you might have trouble finding that tap in the US, much less South Africa. Best to start with the Numrich (Gun Parts) ejector rod knob and modify from there.

Added: Good thing I don't mind being wrong. Midway has both taper and bottoming taps in 6-36, and at much cheaper prices than most on-line hardware stores.
Carbon Steel Taper Tap 6-36 Thread
Carbon Steel Bottom Tap 6-36 Thread

Buck
 

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Discussion Starter #6
OK, finally got to the New Services in the back of the safe, and the ejector rod threads are 6-36, half way between the UNC 6-32 and UNF 6-40. I suppose that Colt wanted their own proprietary thread, but who knows why. I think you might have trouble finding that tap in the US, much less South Africa. Best to start with the Numrich (Gun Parts) ejector rod knob and modify from there.

Added: Good thing I don't mind being wrong. Midway has both taper and bottoming taps in 6-36, and at much cheaper prices than most on-line hardware stores.
Carbon Steel Taper Tap 6-36 Thread
Carbon Steel Bottom Tap 6-36 Thread

Buck
Thanks very much Haggis. Unfortunately I believe that Midway will not supply outside the US. However, my 2008-2009 Brownells catalogue lists 6-36 taps, and they most certainly do supply us here. I will check their website once my internet connection is working at full speed again; it has been down for over two weeks because of cable theft!

Attached is a picture of the head I need to copy. Later ones on World War I 455 Colts are knurled and have two grooves around them and so cannot be easily converted.

Peter
 

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